Two key components of neural regeneration, survival of the involved neurons and elongation of axonal elements, are likely to depend on the availability to these neurons of an appropriate trophic drive. Until recently the only trophic factor known was Nerve Growth Factor which is capable of ensuring both survival and neuritic growth of its targets, namely synpathetic and sensory genglionic neurons. We have very recently identified a new neuronotrophic factor, CNTF, which is capable of supporting the survival of certain cholinergic ganglionic neurons. A quantitative and sensitive bioassay has been established, using monolayer cultures of chick embryo ciliary ganglionic neurons. A source, abundant enough to permit the isolation of the active factor, has been identified in the physiological target of ciliary innervation, the chick embryo eye. CNTF has been shown 1) to reside in the very intraocular structures, which become innervated by the ciliary ganglionic neurons (choroid, ciliary body, iris), and 2) to increase markedly during the developmental period when the target-dependent survival of these neurons is decided in the normal in vivo situation. The eye-derived macromolecular CNTF has already been partially purified to a potency of 15ng/unit, and can be injected in vivo or used in vitro with no apparent toxicity. Therefore, it is now possible to pursue independently from one another several research tasks, namely: 1) in vitro analysis of the cell target spectrum of CNTF, and of the neuronal responses to the factor; 2) in vivo investigation of CNTF effectiveness on ciliary ganglionic (and other cholinergic) neurons, in developmental and regenerative situations; 3) purification to homogeneity and characterization of the CNTF molecule, and production of an anti-CNTF antibody.